Block copolymers have been used widely in the hot melt adhesive industry for a variety of applications. Block copolymers are often the preferred polymer base due to their good heat stability, high cohesive strength, and compatibility with a wide range of tackifiers and plasticizers.
Kraton G-1651, a S-EB-S linear A-B-A block copolymer, having a molecular weight of about 240,000, is intended for use by the injection molding industry for shoe soles. Due to its relatively high molecular weight, it was thought unsuitable for the hot melt adhesive industry.
Chen, U.S. Pat. No. 4,369,284 teaches dimensionally stable gelatinous elastomer compositions. Utility for such compositions include toys, therapeutic hand exercising grips, shock absorbers, acoustical insulators, and other uses. The essential ingredients of Chen consist of high styrene S-EB-S polymer in combination with high levels of plasticizing oil. Since such compositions do not include the use of tackifying resins, and that Chen teaches away from blending such polymers with other polymers, tackifiers, and fillers, such compositions are not useful as adhesives.
Sieverding, U.S. Pat. No. 4,833,193 claims the use of Kraton G-1651 alone or in combination with an ethylene- propylene diblock copolymer, at least 20% of a low molecular weight resin having a ring and ball softening point of about 10.degree. C. to 45.degree. C., and up to 80 weight percent of a mineral oil. Sieverding sets forth that an exceptional feature of his invention is the uniquely high concentration of low molecular weight resins. In the 196 examples set forth, Sieverding does not teach blending Kraton G-1651 with other block copolymers other than an ethylene-propylene diblock copolymer nor does he teach the use of solid tackifiers.
Conventional block copolymers are known and disclosed in various patents such as Collins, U.S. Pat. No. 4,136,699, Malcolm et al., U.S. Pat. No. 5,0547,571 and Raykovitz et al., U.S. Pat. No. 4,704,110.